The complex represented by the following formula (1), i.e., di-μchloro-bis [chloro(η6-1-isopropyl-4-methylbenzene)ruthenium (II)] complex (hereinafter sometimes referred to as “Ru-CPC complex”) is used as a catalyst raw material for a hydrogenation reduction reaction, metathesis reaction or the like (see: Journal of Organic Chemistry, Vol. 59, 3064 (1994) (Non-patent Literature 1); Organometallics, Vol. 18, 3760 (1999) (Non-patent Literature 2); etc.).

As methods for producing a Ru-CPC complex, the following two methods are known. One is a method in which 10 ml of α-phellandrene is reacted with 2.0 g of ruthenium chloride hydrate under the reflux of 100 ml of ethanol for 4 hours, and the reaction mixture is cooled, followed by separating the obtained crystal by filtration (“Jikken Kagaku Koza (Courses in Experimental Chemistry)”, Vol. 21, 5th edition, page 221 (Non-patent Literature 3)). Another is a method in which 200 ml of ethanol, 45 ml of α-terpinene and 22 ml of water are added to 10 g of ruthenium chloride hydrate and the mixture is refluxed for 4 hours, and after that, most of ethanol is removed by distillation, followed by separating the obtained crystal by filtration (Japanese Laid-Open Patent Publication No. 11-322649 (Patent Literature 1)).
α-phellandrene, which is a conventional raw material, is most efficiently and most inexpensively produced by steam distillation from leaves of eucalyptus (Eucalyptus dives Schuer Type). However, the supply is easily influenced by weather, etc. Thus, in terms of stable supply, α-phellandrene has a big problem. Regarding α-terpinene, it can be generally obtained by extraction from a natural product or chemical synthesis. However, because of extraction from a natural product, in terms of stable supply, α-terpinene has a problem. Further, in the case of chemical synthesis thereof, α-terpinene having a purity of 90% or more is not commercially available.
Therefore, there is a problem that the production cost to obtain a high-purity Ru-CPC complex is high.